Which of the following pairs represents types of stereoisomerism?

Which of the following compounds is optically inactive?

The correct statements with respect to the above pair of reactions are that:
$(I)$ The reactions are stereospecific.
$(II)$ $(X)$ is erythro and $(Y)$ is threo isomer.
$(III)$ $(X)$ is threo and $(Y)$ is erythro isomer.
$(IV)$ Each of $(P)$ and $(Q)$ gives a mixture of $(X)$ and $(Y)$.

The product of this reaction should be

Which of the following is an aromatic compound?

Among the given compounds,the correct order of enol content is: